Conveyors, such as escalators, travelators, moving walkways, and the like, provide a moving pathway to quickly and conveniently transport people from one location to another. More specifically, the moving pallets or steps of a conveyor move passengers along the length of the pathway between two landing platforms at predetermined rates of speed. Step chains hidden from view and disposed underneath the conveyor serve to interconnect each of the steps in a closed loop fashion. Driven by a main drive source, drive shafts and associated sprockets, the step chains move the steps along an exposed upper surface of the conveyor to transport passengers between the landing platforms. Sprockets disposed within each of the two landing platforms guide the step chains through an arc to reverse the direction of step movement and to create a cyclic return path.
Because of their continual motion, conveyors are prone to various internal failures, which may further cause injury to passengers on or near the conveyor. One such failure is associated with the speed of the conveyor, or the velocity at which the steps of a conveyor travel between landing platforms. The speed of the conveyor may deviate or fluctuate from a predefined nominal speed causing the steps of a conveyor to move too fast, too slow, stop abruptly, accelerate too quickly, or the like. Inconsistencies in the speed of a conveyor may be caused by several factors. However, in most occurrences, inconsistencies in the speed of a conveyor may be caused by fluctuations in the power supplied to the main drive source of the conveyor. For instance, overvoltage, undervoltage, power surges, spikes, or other inconsistencies in the power supplied to the conveyor, may cause variations to the conveyor which accumulate over time and ultimately offset a predefined nominal speed thereof. Power fluctuations may also hinder the ability of the conveyor to stop within predefined times or distances as required by safety protocols.
Other failures pertain to misaligned or missing pallets or steps. Over time, one or more steps of a conveyor may break loose from the associated step chains causing the steps to drop or fall beneath the conveyor system undetected. Missing steps may also be caused by improper maintenance. Conveyors require periodic maintenance in which one or more steps may be removed, replaced, or the like. However, if a step is not properly fastened or realigned with the step chains, the step may break loose and fall. In any event, if a control system of a conveyor fails to detect a void caused by a missing step, the conveyor may continue to operate, advance the void to the upper surface of the conveyor and expose the void to passengers. Unknowing passengers may fall or step into the void and become injured.
Accordingly, escalators and travelators are provided with various safety measures which serve to minimize hazards caused by such fault conditions. For instance, periodic maintenance may be performed on site by service technicians to ensure proper operation of the conveyor. However, such maintenance is timely, costly and introduces the risk of human error. Other safety measures may employ safety monitoring devices. Specifically, conveyors may be provided with a safety monitoring device which monitors operation of the conveyor for fault conditions. When a fault has been detected, safety monitoring devices may be configured to transmit correctional instructions to a control unit of the conveyor or simply halt operation of the conveyor until the fault is manually cleared by a service technician. However, conveyors may also be required to operate in compliance with safety codes and regulations associated a conveyor type, location, application, and the like. As the type, location and application of each conveyor is different, the safety monitoring device associated with each conveyor must also be different.
In particular, the safety monitoring device for each conveyor must be specifically designed, configured and preprogrammed for that particular conveyor, which amounts to a considerable amount of time and money spent for building each conveyor system. This also means that existing safety devices are not adaptable to any other conveyor type or application, and further, cannot be upgraded to comply with changing conditions, such as new conveyor safety codes and regulations. In order to comply with changing safety codes and regulations, currently existing safety devices, or the conveyor system as a whole, may need to be replaced. Such a service requires a considerable amount of money as well as downtime for the end user.
Therefore, there is a need for a robust and universal control system which monitors the safety parameters of a conveyor system in a more timely and cost efficient manner. More specifically, there is a need for a safety control system that is adaptable to a wide variety of different conveyor types and local safety regulations, and further, monitors conveyor step presence, step speed, stopping distance, and other safety control parameters. Furthermore, there is a need for a control system which automatically determines the operational and mechanical characteristics of an associated conveyor, self-calibrates the necessary safety parameters, and monitors the parameters according to safety codes specific to the conveyor.